Effect of experimental conditions on co-gasification of coal, biomass and plastics wastes with air/steam mixtures in a fluidized bed system

The effect of temperature and of gasification medium was studied, using only air, only steam and mixtures of both as gasification medium, with the aim of optimising co-gasification of coal and wastes. The rise in gasification temperature promoted hydrocarbons further reactions, leading to a decrease in tars and hydrocarbons contents and an increase in H2 release. Increasing temperature, from 750 to 890 °C, during gasification of a mixture with 60% (w/w) of coal, 20% of pine and 20% of PE wastes, led to a decrease in methane and other hydrocarbons concentration of about 30 and 63%, respectively, whilst hydrogen concentration increased around 70%. Hydrocarbons contents decrease was also achieved by increasing air flow rate, because partial combustion caused by oxygen decreased tars and gaseous hydrocarbons, with even a decrease in heating requirements. However, the presence of air is disadvantageous, because it decreases the higher heating value of the gasification gas, due to nitrogen diluting effect. The rise of steam flow rate has proven to be advantageous, because reforming reactions were favoured, thus hydrocarbons concentrations decreased and hydrogen release increased.